The goal of this proposal, is to obtain fundamental information with regard to the structural and functional organization of the walleye dermal sarcoma virus (WDSV). We will utilize these data to examine the epidemiological and molecular mechanisms responsible for the development and regression of tumors in both experimental and natural infections of walleyes. Using defined, molecular and immunological probes, we will follow the fate of WDSV DNA, RNA and viral proteins in these tumors. In addition to providing information as to the prevalence of infection in natural fish populations, data from these analyses should provide further insights into the molecular mechanisms responsible for tumorigenesis. We propose to determine the complete nucleotide sequence of a full-length molecular clone of WDSV. This will be accomplished using the Sanger dideoxy sequencing procedure and will provide a foundation data base for subsequent identification of transcriptional processing signals, and the presence of nonstructural viral accessory genes. Northern blot analysis and the construction and sequencing of viral cDNAs will be used to establish a precise transcriptional map of the WDSV genome. We place heavy emphasis on this approach in that our current data support the hypothesis that a viral-encoded function, analogous to TAX and TAT of HTLV-1 and HIV, respectively, is responsible for tumor induction in walleyes. Concurrent with these studies, we propose to investigate the in vitro tropism of WDSV through infection studies and DNA transfection experiments. A major aim will be to establish a cell culture system for WDSV and use this system to investigate transcriptional regulation and to characterize biologically active molecular clones of WDSV. To carry out these studies we plan to develop specific immunological reagents to follow the fate of virus, both in vivo and in vitro. An extension of the current in vivo transmission studies will identify the in vivo cellular targets of WDSV, routes of infection and eventually allow for induction of tumors by well-characterized viral molecular clones.